Removes nearly 2 times more contaminants.One time upgrade for a lifetime of improvement.Installs in minutes with no tools required.Easy to change filter system.Aprilaire Upgrade Filter Kit 1413 includes replacement filter #413.Fits in units with plastic ( non-metal) doors.

The Aprilaire Upgrade Kit 1413 also replaces the 4272 inner housing previously found in the Aprilaire Model 2400 Air Purifier.